The Performance Over Time chart shows  you how  to see how your performance for each key metric varies over time. 

Click on a metric to see its performance - you can plot more than one to make comparisons between the different aspects of your business. 

Underneath the metrics are more detailed options... for instance instead of rating value, you can also see the Average Transaction Value or Spend Share for each metric. 

Use the other buttons to add 'Events' or change the time scale that the chart displays.